"America stands by its allies, including Australia of course, and we stand by the United States," Mr Turnbull told 3AW.

"So be very, very clear on that. If there's an attack on the US, the ANZUS Treaty would be invoked and Australia would come to the aid of the United States, as America would come to our aid if we were attacked."

The Prime Minister reiterated the same point later in the day after receiving a briefing on North Korea from military and intelligence officials in Canberra.

"Once again, we call on the North Korean regime to stop its illegal, reckless, provocative conduct which is putting the peace and the stability of the region at risk," he said.

Mr Turnbull said Australia and the US both still believed tough new sanctions on North Korea could force the regime to abandon its nuclear weapons program.

"[The Vice-President's] view and the view of the administration is that the way to resolve the situation with North Korea … is through these economic sanctions. That's the preferred way to deal with it," he said.

"But of course if North Korea decides to carry out some of its violent threats then obviously terrible consequences will follow, and there's no point ducking that inevitable consequence."

'Target on our back'

The Prime Minister used stronger language on North Korea than the Foreign Minister.

Yesterday, Julie Bishop said there was no "automatic trigger" for Australia to join a war between the US and North Korea, because Australia was not a party to the armistice declared at the end of the Korean War in 1953.

She acknowledged the ANZUS treaty imposed separate obligations on both countries but also said it only required Australia and the US to "consult" with each other, if either country was threatened or attacked.